Stepped Leader in Lightning

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On September 13, I gave a short reply to JL on the iniation of a  
lightning stroke. Here is the text:

A stepped leader starts in the cloud and reaches towards the earth. When  
it
gets close, a streamer reaches up from the earth. When it reaches the
leader, a conductive path is formed that allows the discharge from the
cloud to the ground. Here are some videos in slow motion:

Sprites, Jets, and Glowing Balls: The Science of Lightning

https://www.youtube.com/watch?v=fzNk4w2k2h0


How does lightning work? Where does it come from? | Weather Wise S2E2

https://www.youtube.com/watch?v=9K-v-RJ-z2A


Lightning Strike at 103,000 FPS
- in Singapore

https://www.youtube.com/watch?v=qQKhIK4pvYo


Lightning in Super Slow Motion

https://www.youtube.com/watch?v=RLWIBrweSU8


This left the question what is a stepped leader? I came across an article  
that gives a good description. I'll give the text here, but check out the  
link. It has good pictures that explain better.

"Inside a thunderhead, electrical charges become separated. Warm
updrafts sweep positive charges aloft, leaving the bottom of the
cloud negatively charged. The attraction between the ground and the
negative charges in the bottom of the cloud creates the lightning
stroke, a brief current of negative charge that travels from cloud
to ground.

The awesome power of the lightning stroke originates in the
thunderstorm cloud where charges somehow become separated. There are
several complicated theories that try to explain the actual
mechanism of this charge separation, but no one really knows what
pulls the charges apart in a thunderstorm cloud. It is believed that
somehow water drops in the cloud become negatively charged and,
being heavier than the surrounding air, fall to the bottom of the
cloud. Meanwhile, the positive ions left behind are swept upward to
the top of the cloud by the warm updrafts within the thunderhead. As
more and more charges separate, parts of the cloud become so highly
charged that the electrical forces tear nearby air molecules apart,
making more charged fragments.

Since the ground beneath the cloud has far fewer negative charges on
it than the bottom of the cloud, there is an attraction between the
ground and the bottom of the cloud. Therefore, any electrons
liberated near the cloud are pulled down toward the ground. As these
electrons move, they bash into air molecules that are in their way,
breaking the molecules up and creating more charged fragments. All
the new negative fragments are dragged downward along with the
original electrons and we have the makings of an electrical
avalanche.

The avalanche would continue unabated were it not for the heavier
and more sluggish positive charges that are left behind. They tend
to attract the accelerating army of electrons back toward the cloud.

But more electrons are continually being liberated up in the cloud,
and they stream to the rescue of the slowing electrons below,
reinforcing their race downward. This process of electrons slowing
and then being rescued by reinforcements repeats itself over and
over again.

Stepped Leader

The initial party of electrons makes its way in jerky 150-foot steps
along a sinuous path toward the ground.

This initial exploratory mission forms what is called a "stepped
leader," named for its start-stop motion. The stepped leader takes
about 5/1000 of a second, moving at about 240 miles per second, to
reach from cloud to ground. When the leader gets near the ground, it
may draw a stream of positive charges (called a streamer) up from
the ground to meet it. When either the stepped leader reaches the
ground or a streamer runs up to join the stepped leader, an
electrical connection is completed between the cloud and the ground.

The ionized air molecules of the leader conduct electricity quite
well, and the path of charged particles acts as a wire, connecting
the highly negative cloud and the positive ground. This ionized air
becomes the path of the main bolt of lightning.

The first charges to feel the connection are those near the ground.

The light and mobile negative charges quickly accelerate along the
wire of ionized air. In their mad rush to the ground the negative
charges collide with the air, causing it to glow like a neon
sign--only thousands of times brighter and with a bluish-white
color. The air near the ground is the first to start glowing, but as
the electrons further and further up feel the connection and begin
to accelerate, the air further and further up also starts to glow.

Even though the negative charges all move from cloud to ground, the
bright flash of lightning moves from ground to cloud in a speedy
1/10,000 of a second, moving 61,000 miles per second! The
super-heated air expands outward explosively, producing the shock
wave we hear as thunder. The bright flash of glowing air is called
the return stroke since it moves from ground to cloud, opposite to
the moving charges.

The return stroke discharges a region of the cloud, but the cloud
can reorganize quickly and as many as 40 strokes have been observed
to use the same charged channel. If you've been told that lightning
never strikes twice in the same place, don't believe it! Lightning
usually strikes more than once!

There is quite a lot of energy in a lightning stroke, about 250
kilowatt-hours. At the current cost of energy, this would be about
$16.75 worth. Doesn't sound like much, but with that amount of
energy, you could lift a 2000-pound car 62 miles high!

Lightning doesn't always travel from cloud to ground. If two parts
of the cloud are charged highly (and oppositely), a lightning bolt
can actually occur inside the cloud. Lightning can also arc from one
cloud to another.

lightning strike

The typical type of lightning is called streak lightning, or forked
lightning. (Photo to the right from NASA - Marshall Space Flight
Center.) If the lightning channel is blown by the wind during a
multiple discharge, each succeeding stroke is displaced by a short
distance, making it appear as ribbon lightning. On rare occasions
the lightning seems to break up into beads that persist for as long
as one second, an unexplained form called bead or chain lightning.

Sometimes the lightning flash is obscured by clouds, which are then
brightly illuminated. During this sheet lightning, the flash seems
to come from everywhere. The most controversial form of lightning is
ball lightning. Ball lightning has never been observed
scientifically and many doubt its existence altogether. It is
reported to occur with or right after a nearby lightning stroke and
is described as a luminous ball of light that floats along fences,
rooftops, or through the open air. The jury is still out on ball
lightning.

https://www.exploratorium.edu/ronh/weather/weather.html

Re: Stepped Leader in Lightning

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It's impressive that nobody understands lightning.

Ground strikes can be positive or negative.  



Re: Stepped Leader in Lightning

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[...]

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It's improving. I used to think a lightning bolt had to cover the entire  
distance from the ground to inside the cloud, perhaps trillions of volts.

The stepped leader is a much better explanation. The ionized channel  
behind the leader is conductive, so it greatly reduces the voltage  
necessary to form a lightning bolt.  

The steps occur in jumps of about 150 feet, so the breakdown only has to  
go that far. Still takes a lot of voltage, but not nearly the miles of  
the previous understanding.

Re: Stepped Leader in Lightning
On Thursday, October 1, 2020 at 12:19:23 PM UTC-7, John Larkin wrote:

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Don't be silly!  Avalanche in solids (like a Zener diode) or gasses (Geiger tubes, to
name the old examples) are well-studied in a variety of materials and regimes.
Nobel Prize 1992 went to Georges Charpak for this subject.

Large scale and atmospheric chemistry are... minor details.

Re: Stepped Leader in Lightning
On Thursday, October 1, 2020 at 4:58:33 PM UTC-4, whit3rd wrote:
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Last I read there were/are uncertainties in the charge separation
mechanism.  

George H.  

Re: Stepped Leader in Lightning
On Thu, 1 Oct 2020 19:22:56 -0700 (PDT), George Herold

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The common phrase in the Wiki article on lightning is "For reasons not
well understood,..."

The x-ray and gamma radiation from lightning aren't understood either.




--  

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

We've slightly trimmed the long signature. Click to see the full one.
Re: Stepped Leader in Lightning
On Friday, October 2, 2020 at 1:09:27 PM UTC+10, jla...@highlandsniptechnol
ogy.com wrote:
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iger tubes, to  
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regimes.  
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It's stinking hot plasma. Even if the X-rays and gamma rays were just the h
igh energy tail of a thermal distribution of emitted photons, they wouldn't
 take much understanding. As it is, you've got ionised atmospheric gases -  
including water vapour - and free electrons (which do most of the conductio
n since they move faster than the - much heavier - ions).  

We may not understand it in terms of having a detailed species-by-species i
nventory of the ions and electrons in the hot channel, but there's no parti
cular mystery about seeing the  the occasional high energy photon get emitt
ed.

--  
Bill Sloman, Sydney

Re: Stepped Leader in Lightning
snipped-for-privacy@highlandsniptechnology.com wrote:

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What article are you referring to?

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A great deal is understood about lighting, from high speed videos to  
actual flights inside thunderstorms. A more generous term might be  
"details are still being studied". See Wikipedia

https://en.wikipedia.org/wiki/Lightning

See Also

https://en.wikipedia.org/wiki/Thunderstorm

Thunderstorms and lightning are fascinating topics. As engineers, it  
behooves us to learn as much as possible in order to minimize the  
destructive effects of nearby strikes.

Re: Stepped Leader in Lightning
On Thursday, October 1, 2020 at 11:56:15 PM UTC-4, Steve Wilson wrote:
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This looks OK.  Many of the hits I got searching google were for papers
from the 60-80's.  
http://www.phy.olemiss.edu/~jgladden/phys510/spring06/Gurevich.pdf

George H.  
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Re: Stepped Leader in Lightning
George Herold wrote:
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A major mystery was how the lightning leader is initiated inside the  
storm cloud - i.e., what starts the initial spark breakdown process. The  
measured E-fields in thunderstorms are too low to trigger the avalanche  
breakdown processes that are necessary for initial spark breakdown and  
stepped leader formation. It now appears that cosmic ray showers play a  
role by creating showers of high-energy electrons ("runaway electrons"  
that initiate the avalanches that culminate in streamers and then leaders.


Re: Stepped Leader in Lightning

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I have heard the same thing also. An additional effect is noted in the  
jerky and random changes in direction of the stepped leader due to cosmic  
rays.


Re: Stepped Leader in Lightning
Am 01.10.20 um 22:58 schrieb whit3rd:
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Avalanche diodes are NOT Zener diodes.
Prof. Zener even sued against his name being used for this.
They settled to call them Z-Diodes and attribute it to the form of the  
curve.


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Cheers, Gerhard

Re: Stepped Leader in Lightning
On Friday, October 2, 2020 at 11:43:17 PM UTC+10, Gerhard Hoffmann wrote:
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ger tubes, to
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egimes.  
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What are sold as "zener diodes" ranges from actual Zener diodes which have  
breakdown voltages below 5V to avalanche diodes which break down above this
.

Around 5V  both mechanisms.  are going on in parallel. Low voltage regulato
r diodes in which the Zener mechanism is dominant have a negative temperatu
re coefficient, while higher voltage regulator diodes have a positive tempe
rature coefficient, but if you want a low temperature coefficient regulator
, a roughly 5.6V avalanche diode in series with a forward biassed diode - a
s in the 1N821 to 1N829 series - is the usual choice, giving you a distribu
tion between 5.89V and 6.51V centered at about 6.2V at 7.5mA.  If you want  
to get stability you pay for in a 1N829, you have to be very careful to kee
p the current very closes to 7.5mA

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I don't think that anybody gets too excited about the name.

<snip>

--  
Bill Sloman, Sydney  


Re: Stepped Leader in Lightning
wrote:

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Everybody calls them zeners.  


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That sure didn't last long.



--  

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

We've slightly trimmed the long signature. Click to see the full one.
Re: Stepped Leader in Lightning
Am 02.10.20 um 17:48 schrieb snipped-for-privacy@highlandsniptechnology.com:
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Just a case of honesty. Does not fit into today's world.


Gerhard


Re: Stepped Leader in Lightning
wrote:

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What should we call a 5.2v diode?

Zenalanche? Avazar?

Should Digikey have three catagories?





--  

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

We've slightly trimmed the long signature. Click to see the full one.
Re: Stepped Leader in Lightning
On Saturday, October 3, 2020 at 12:07:25 PM UTC+10, snipped-for-privacy@highlandsniptechnology.com wrote:
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Try voltage regulator diode. "Zener diode" has worked for as long as I've known about them (which is some 55 years now). It might not be technically accurate, but it's demonstrably good enough for practical use.
  
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Why should they bother? Who would it help? And how?

--  
Bill Sloman, Sydney

Re: Stepped Leader in Lightning
On a sunny day (Thu, 01 Oct 2020 19:09:05 GMT) it happened Steve Wilson

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I have seen ball lightning face to face in my high-school years.
One day, just after I placed an FM reception dipole on the neighbors roof,
a big lightning storm started. Told him to disconnect the antenna,
I was on the first floor, the other neighbor below us had a long wire antenna in his garden.

I had the window open, looking at the lighting...
After some bang a big white ball, about 30 cm or so in diameter, appeared and hung before the window.
Looked at it face to face, from maybe about 1 meter distance, no heat coming from it.
It hung there a few seconds, and then slowly started sinking and a load bang happened.
Next morning went to look at the antenna in that garden, was between 2 trees, only 2 black burned ends were left,
the ball evaporated it.
Look up Murat Ozer electron black hole:
 https://arxiv.org/abs/gr-qc/9911011


I was almost a magic experience, sort of 'will it come to me or?' well, I take
it as nature showing me something, plenty of discussions in sci.physics about that years ago.

Re: Stepped Leader in Lightning
PS
that was in the days when we were experimenting to control things with our thoughts.
Take it as sign to me perhaps,
Had some experiences before that, this was a day or so after that.
Everything is connected.

We really know shit.
:-)







Re: Stepped Leader in Lightning
On 10/2/2020 1:00 AM, Jan Panteltje wrote:
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But not much else.


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